Project Summary Proposed is a five-year research career development plan focused on evaluating the role of intratumoral (IT) administration of chemokine (C-C motif) ligand 21 (CCL21)-gene modified human monocyte-derived dendritic cells (DC) plus pembrolizumab for the treatment of advanced non-small cell lung cancer (NSCLC). The candidate is an Assistant Professor of Medicine in the Division of Hematology/Oncology at The University of California, Los Angeles (UCLA). The proposal builds on the candidate?s previous translational research and clinical experience in lung cancer immunotherapy by incorporating (1) formal training in clinical/translational research via The Master of Science in Clinical Research Program, (2) conduct of a phase I clinical trial, and (3) evaluation of clinical and correlative data generated on trial. Under the tutelage of his Primary Mentor, Steven Dubinett, M.D., a successful mentor of more than 45 trainees, and strong Mentorship Committee of David Elashoff, Ph.D. and Edward Garon, M.D, M.S., the candidate will gain the skills necessary to become an independent physician scientist. Importantly, he also has strong institutional support to foster his development. Lung cancer is the most common cause of cancer-related mortality in the United States. Programmed cell death-(ligand)1 [PD-(L)1] agents, such as pembrolizumab, have revolutionized treatment of the disease, but a significant proportion of patients still do not benefit. The most commonly proposed reason for the lack of anti- PD-(L)1 efficacy is the absence of tumor infiltrating lymphocytes. One potential approach to overcome this limitation is to utilize in situ vaccination with IT injection of functional antigen presenting cells, such as CCL21 modified DCs, since this chemokine promotes (1) co-localization of lymphocytes and DCs and (2) facilitates T lymphocyte activation. A phase I trial evaluating IT administration of autologous CCL21-DC in advanced NSCLC patients revealed that the procedure is safe, feasible, and promotes effector T lymphocyte infiltration, in addition to systemic immune responses. However, increased PD-L1 expression was observed in the tumor microenvironment following IT injection, suggesting the PD-1 immune checkpoint may be forestalling a more robust CCL21-mediated antitumor response. As a result, it is hypothesized that combined IT CCL21-DC plus pembrolizumab will improve clinical outcomes in patients with advanced NSCLC. The aims of this proposal are to (1) complete a phase I trial of IT CCL21-DC plus pembrolizumab in patients with advanced NSCLC and evaluate (2) blood and (3) tumor tissue collected on trial via mass cytometry (CyTOF) and multiplex immunofluorescence (MIF), which will be guided by the results of four additional correlative analyses planned on trial, to further elucidate remodeling of immunologic pathways as a result of this novel therapeutic approach.